U.S. Pat. No. 4,411,889 discloses a system of topical fluoride treatment in the oral cavity which combines the advantages of an application of a solution with those of a gel. The patent describes a fluoride-containing, self-gelling aqueous composition for topical application on tooth surfaces in the oral cavity for the prevention of dental caries. The self-gelling composition comprises a low-viscosity liquid aqueous composition of a monomer or prepolymer of an alkyl such as ethyl orthosilicate (also known as tetraethoxy silane (TES)), a water-soluble fluoride compound to inhibit or prevent dental caries and a gelation agent, such as a fluoride compound and a surface-active agent to provide for the in situ gelation of the composition from a low-viscosity liquid composition to a gelled state. Typically the gelation occurs from a liquid to a gel state in a time period of about one hour or less after mixing through the hydrolysis of the orthosilicate. The self-gelling transformation at a neutral pH is favored by high concentration of the fluoride, which acts both as a caries preventative agent and as a gelation facilitating agent, ammonium ions, intensified emulsification and temperature increase. The self-gelling composition usefully employs a variety of surface-active agents such as those agents, such as sodium lauryl sulfate, cetylpyridinium halides, and nonionic agents, such as the polyoxyethylene derivatives of fatty acid esters of sorbitol anhydrides. Optionally, the self-gelling compositions may include buffering agents, viscosity increasing agents, while preferred compositions employ a water soluble fluoride in combination with a surface-active agent.
U.S. Pat. No. 4,411,889 and the co-pending application Ser. No. 518,951 also describes the employment of various drug compounds in place of the fluoride dental caries preventative agent, so as to provide for a self-gelling composition for the sustained release of the drug compound. The self-gelling, drug-containing aqueous system is typically used for topical applications, both in the oral cavity; for example, in periodontal pockets, as well as for human and veterinary use, such as for the treatment of mastitis by the application of a topical coating to the affected area. The self-gelling composition provides for the sustained release of an antibiotic, antibacterial or other therapeutic drug compound. The self-gelling aqueous composition typically comprises, but is not limited to, an emulsion of the ethyl orthosilicate as a monomer or prepolymer in an amount of about 5 to 30 percent by weight, drug compound selected for its therapeutic effect which may or may not be water soluble and a gelling facilitating agent, typically a surface-active agent, generally in an amount of from about 0.01 to 2 percent by weight of the composition. The composition is a low viscosity liquid system generally having a pH of 3 to about 8.5 and typically 6 to 7, which after vigorous mixing and on topical application changes the state from a liquid to a gel in a time period from about 1 hour or less.
It is desirable to provide for a self-gelling liquid composition which contains a wide variety of therapeutic compounds for topical application and which has accelerated gelling time.